Developing Tests to Distinguish Between Similar-Looking Unknowns

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Learners identify an unknown liquid by comparing its behavior to known liquids. Learners drop liquids onto different surfaces and see how the liquids behave. Learners realize that using a combination of results from two or more tests will allow them to successfully identify the unknown. Use the related activity "Look-alike Liquids" from the same resource (see related resources) to introduce the behavior of the liquids on different surfaces. [Activity is publicly available through a web crawler capture on Activity write-up only, images are unavailable.]

Quick Guide

Preparation Time:
5 to 10 minutes

Learning Time:
30 to 45 minutes

Estimated Materials Cost:
1 cent - $1 per group of students

Age Range:
Ages 8 - 14

Resource Types:
Activity, Experiment/Lab Activity


Materials List (per group of students)

  • Tap water in cup
  • Isopropyl rubbing alcohol (70%) in cup
  • Detergent solution in cup
  • Salt water in cup
  • 1 Additional small cup
  • 5 Droppers
  • Construction paper
  • Notebook paper, copy paper, or newspaper
  • Brown paper towel
  • Wax paper
  • Pencil
  • Student Activity Sheet


  • Mathematics
    • Data Analysis and Probability
      • Data Analysis
      • Data Collection
    • Measurement
      • Units of Measurement
  • Physical Sciences
    • Chemistry
      • Solutions
    • States of Matter
      • Liquids
  • The Nature of Science
    • The Scientific Process
      • About Inquiry
      • Asking Questions
      • Conducting Investigations
      • Gathering Data


To use this activity, learners need to:

  • see
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


Components that are part of this resource:

This resource is part of:

Access Rights:

  • Free access


  • Kessler, James H. ; Galvan, Patricia M.


  • All rights reserved, American Chemical Society, 2007